Updated

James ‘Whitey’ Bulger, the man accused of being a top-level FBI informant who secretly ratted on the Italian Mafia and other criminals, was reportedly reprimanded in court Thursday morning after calling a former FBI investigator a ‘(expletive) liar’ while the investigator was on the witness stand.

Brian Kelly, the assistant U.S. attorney, overheard the remark and raised the issue while jurors were outside the courtroom, The Boston Herald reported.

"I know he spent his whole life trying to intimidate people in South Boston, including 15-year-old boys in South Boston," Kelly said, according to the report.

An attorney for Bulger said he would address the issue with his client.

Attorney Hank Brennan kept up an aggressive cross-examination Wednesday of an official with the Justice Department's Office of the Inspector General. Prosecutors called the official to testify in Bulger's racketeering trial to introduce Bulger's FBI informant file.

Bulger is accused of playing a role in 19 murders in the 1970s and `80s while allegedly running the Winter Hill Gang.

The 83-year-old has pleaded not guilty and his lawyers have strongly denied that he was an FBI informant.

The defense contends that former FBI Agent John Connolly fabricated Bulger's FBI file in an attempt to cover up his own corrupt behavior.

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The Associated Press contributed to this report